Quadrature combined amplifiers are widely used in power amplification applications in microwave and radio frequency (RF) spectrum. The advantage of the quadrature combined amplifier is that optimum impedance matching can be done for low noise, gain flatness, and power and linearity while the input and output return loss (VSWR) will be good as long as the two single ended amplifiers (within the quadrature amplifier) are identical. Quadrature combined amplifiers are also commonly used rather than single ended amplifiers for multiple cascaded stages due to the low interaction and enhanced stability because of the good input and output return loss. Also, the quadrature combined amplifier is less sensitive to load mismatch and more reliable in operation than the single ended amplifier. Furthermore, there are a variety of other application areas where the quadrature combined amplifier is used, such as, microwave heating, driving another high power source, driving a transmitting antenna, exciting resonant cavity structures, and so forth.
Existing RF amplifying systems based on quadrature combined amplifiers use a directional coupler to obtain an RF coupled output with directivity. The directional coupler is bulky and may have an undesirable impact on the size and the overall cost of the RF amplifying system. In light of the above, there is a need of a system that reduces overall size and cost of the RF amplifying system.